I presented the sealed relay switched version

Where did you present that, and how is the relay controlled?

 

Where dis you present that, and how is the relay controlled?

I provided a very detailed text description in post#25. A wire by wire connection description.
The relay is controlled by a switch engaging the negative connection to the opposite end of the relay coil from where the + 12 volt supply is connected. The negative return connection is thru the shield of the 4 conductor shielded cable. The relay that I suggested has a graphic of the actual connections printed on the case.

 

I provided a very detailed text description in post#25.

OK, I missed that.
So wouldn't it be better to use a latching relay as I proposed, with a push-button at each location to select the active pot?

But if you think a normal relay is better, than it's not clear to me that the switch between cab and remote can be controlled from either location with your configuration.
To do that, you could control the relay coil with two SPDT switches, one at each location, connected as a 3-way switch.
A light at each location could indicate which location is active.

 

OK, I missed that.
So wouldn't it be better to use a latching relay as I proposed, with a push-button at each location to select the active pot?

But if you think a normal relay is better, than it's not clear to me that the switch between cab and remote can be controlled from either location with your configuration.
To do that, you could control the relay coil with two SPDT switches, one at each location, connected as a 3-way switch.
A light at each location could indicate which location is active.

NO, it would not be a benefit because it could happen that the remote was selected and then the remote connection failed. that would leave no control available until somebody altered the selection. With the single switch operating the relay, if the connection is lost the control defaults to the other control rapidly. AND, latching relays cost more and are less reliable.

 

it could happen that the remote was selected and then the remote connection failed. that would leave no control available until somebody altered the selection

Don't see that as a significant problem.
Just push the button at the other location to energize it, if a location fails.

latching relays cost more and are less reliable.

Can't believe that cost would be significant in this application.
And what is the basis for your claim that they are less reliable?

 

Don't see that as a significant problem.
Just push the button at the other location to energize it, if a location fails.
Can't believe that cost would be significant in this application.
And what is the basis for your claim that they are less reliable?

More mechanical components make them, by definition, less reliable. The other issue is that pressing buttons to change states of a system does not provide any visual indication as to which state is selected. A two position switch is clearly in one position or the other.

 

I like the motorized potentiometer solution best because it satisfies all the requirements except you do not turn anything you push one of two buttons on each end. This would be very reliable also, and always start the 'pump' from the same flow rate as it was set from either end previously, which I think is a very important requirement. We can't have someone come over and turn a pot and suddenly it jumps up to some super-fast flow rate, and maybe not even a super low flow rate. I like to call this the "sync'ing" requirement.

I do not believe anyone not qualified should be doing this job though. An engineer needs to review everything and make some important, far-reaching decisions.

 

I like the motorized potentiometer solution best because it satisfies all the requirements except you do not turn anything you push one of two buttons on each end. This would be very reliable also, and always start the 'pump' from the same flow rate as it was set from either end previously, which I think is a very important requirement. We can't have someone come over and turn a pot and suddenly it jumps up to some super-fast flow rate, and maybe not even a super low flow rate. I like to call this the "sync'ing" requirement.

I do not believe anyone not qualified should be doing this job though. An engineer needs to review everything and make some important, far-reaching decisions.

I DID review it. And AM qualified.

 

Relays are not required, they are simply a further complication,
something else to cause more confusion and points of failure.

The Engine RPM is not used to vary the flow-rate of water.

The Engine is possibly being slowed-down to
prevent Steam-Generation inside the Pump
when there is zero-Water-flow through the Pump due to a Valve being closed.
This Steam-Generation can become a very serious problem, and actually melt Seals, Hoses, etc.

The Engine-RPM can easily be heard, and possibly,
the RPM can also be felt as a physical-vibration throughout the Truck.
Just the irritation of listening to the Engine continuously running wide-open "may be"
one of the reasons for wanting Remote-Control.

We still have not been informed as to WHY Remote Engine-Speed Control is desired by the Thread-Starter.
My guess is that it is because of one, or both, of the reasons described above.
There may be other reasons as well,
such as, permanently-mounted, side-spray Water-Nozzles, powered by the Pump in question,
that need to be controllable remotely while driving.

The original question posed by the Thread-Starter may have no practical application
towards achieving what is actually needed and wanted by the end-users of the proposed Remote-Control.
A completely new approach may be needed.
.
.
.

 

More mechanical components make them, by definition, less reliable.

Don't see that a latching relay has significantly more "components" then a non-latching one, other then some added magnets and possibly an extra coil.

The other issue is that pressing buttons to change states of a system does not provide any visual indication as to which state is selected.

You don't need a visual indication.
The push-button does not alternate the states, it picks the state which makes the pot next to the push-button active.
So if moving the pot doesn't affect the speed, the operator just pushes the button, and then it will affect the speed.

 

Relays are not required, they are simply a further complication,
something else to cause more confusion and points of failure.

The Engine RPM is not used to vary the flow-rate of water.

The Engine is possibly being slowed-down to
prevent Steam-Generation inside the Pump
when there is zero-Water-flow through the Pump due to a Valve being closed.
This Steam-Generation can become a very serious problem, and actually melt Seals, Hoses, etc.

The Engine-RPM can easily be heard, and possibly,
the RPM can also be felt as a physical-vibration throughout the Truck.
Just the irritation of listening to the Engine continuously running wide-open "may be"
one of the reasons for wanting Remote-Control.

We still have not been informed as to WHY Remote Engine-Speed Control is desired by the Thread-Starter.
My guess is that it is because of one, or both, of the reasons described above.
There may be other reasons as well,
such as, permanently-mounted, side-spray Water-Nozzles, powered by the Pump in question,
that need to be controllable remotely while driving.

The original question posed by the Thread-Starter may have no practical application
towards achieving what is actually needed and wanted by the end-users of the proposed Remote-Control.
A completely new approach may be needed.
.
.
.

Really, post #1 Mentioned a "12 volt control circuit" for a motor. It did not say a 12 volt motor. IF it had stated " a 12 volt control system for a 23 HP ENGINE then no PWM schemes would have been presented, probably.
And if the person at the rear of the ruck is fighting a fire they do not want to be pressing buttons. Just twist a knob to get more flow. Then turn it down when it is time to move a bit. AND, mashing buttons while wearing protective gloves can be a challenge.

 

A Single Actuator Button, at each location is all that is needed,
aside from 2 Resistors and some Cat-5-Cable.
Push-On / Push-Off
.
.
.
This is not hard to push even with Welding-Gloves on ................
.

 

Really, post #1 Mentioned a "12 volt control circuit" for a motor.

Read the thread title.

 

From a systems point of view, I think that two switch selectable pots at each end of a truck controlling a biggish motor risks switching between one set to minimum and the other set to maximum which may not damage anything but is not ideal.

If I was to do this I would use the existing single pot, replaced with electrically controllable pot (either motorised or solid state), controlled by rotary encoders at each end of the truck: the motor is running and either knob turns the speed up or down from it's current setting depending on direction of knob action. Very simple to use operationally.

Or even use a lever operated cable linkage from end to end with cable over a pulley on the speed knob. All mechanical.

Of course, if 'high' and 'low' are the only settings really required, then a button at each end that flips the speed between two settings is quite adequate.

 

The Thread-Title is merely someones idea of what "might-work".
It is not self-explanatory or obvious to anyone.
.
.
.

 

This thread is a perfect example of the XY problem.

https://xyproblem.info/

 

This thread is a perfect example of the XY problem.

It started out that way for sure. Most of them do.

 

This is why I ask questions. I learned that many years ago, to always ask the questions early, not only to be sure to get an adequate understanding, but also to avoid looking dumb much later in the process of providing a solution.

The issue with alternate action push buttons is always that what they do when pushed depends on what action they have done the last time they were pressed.

 

This is why I ask questions. I learned that many years ago, to always ask the questions early, not only to be sure to get an adequate understanding, but also to avoid looking dumb much later in the process of providing a solution.

The issue with alternate action push buttons is always that what they do when pushed depends on what action they have done the last time they were pressed.

And that's the way it should be. Why shouldn't it be that way.
If you step on the gas pedal of your car and it goes 25mph, do you want it to suddenly jump up to 50mph.
If there were two gas pedals in a car and two 'drivers', driver 1 steps on their gas pedal and the car goes 25mpg, then the other driver presses their gas pedal and the car suddenly jumps up to 50mph, does that sound reasonable even though the other driver only pressed the pedal a little bit, and that was just after the pedal was pressed just after that.

That's why I called this issue the sync'ing problem. I would expect either user to want to change the speed from whatever it was to whatever they want it to be now. For example, I do not think it would make any sense to want to turn it all the way down and then have to turn it all the way back to whatever the second user wanted it to be even if it's just a tiny bit faster. In other words, lets say it is running at 100rpm, and the second user wants 200rpm. They should be able to turn it from 100rpm to 200rpm, not from 100rpm down to 0rpm then up to 200rpm, for example. Once it is at 200rpm, the first user should be able to turn it from 200rpm to 300rpm, or from 200rpm to 150rpm, for example. The set point should start from the previous set point so there are no instantaneous jumps in speed.

 

I DID review it. And AM qualified.

Hi,

You mean you are willing to take responsibility for the workings of fire trucks for two entire countries? That's guts